Evaluation of grain yield, yield components, oil and some agronomic traits of safflower cultivars on winter sowing different dates of in Sistan region

Introduction
Planting date is considered to play a crucial role in decision-making processes of crop production and management, especially in the areas where plants are impacted by deleterious factors such as terminal cold and drought, early drought stress and extreme heat (Behdani & Jami Al-Ahmadi, 2008). In the studies conducted in different regions, delay in planting time in both autumn and spring resulted in decreases in grain, and oil yield, number of seeds per head, number of heads per plant, 1000-seed weight, plant height, number of leaves per plant, and dry weight of shoot (Solhe oskouei et al., 2016 ; Deltalab et al., 2011). Therefore, this experiment was performed to find the best winter sowing date for different cultivars and to investigate changes in grain yield, yield components and oil of safflower cultivars under delayed cultivation.
Materials and Methods:
The experiment was carried out in a split plot arrangement based on randomized complete block design with three replications in two years, 2013 and 2014 at Zahak Agricultural and Natural Resources Research Station, Sistan and Baluchestan province. The main plot consisted of five sowing dates including: 21th Dec., 9th Jan., 29th Jan., 19th Feb. and 10th Mar. and the subplot was assigned to four cultivars; Golldasht, Padideh, Faraman, Gollmehr, which were independently randomized. In this study, yield characteristics and components of grain yield, agronomic and phonological traits in addition to grain oil content were investigated. Statistical analysis was performed using MSTAT-c software.
Results & Discussion:
The combined analysis of variance indicated significant effect of year, and cultivar on the all traits phenological, morphological, grain yield and its components as well as oil content. Goldasht and Faraman cultivars, at all the sowing dates, showed shorter time to physiological maturity. The highest mean of plant height (114 cm) was observed at the first sowing date (21th Dec.), which was 20% and 28% higher than the fourth (19th Feb.) and the fifth (10th Mar.) sowing dates, respectively. Padideh and Golmehr cultivars showed the highest plant height. Grain yield in the first year increased by 6% relative to the second year. The seed yield at the first sowing date (21th Dec.) was 1611 kg.ha -1, which was 16%, 24%, 37% and 44% greater than at the second (9th Jan.), the third (29th Jan.), the fourth (19th Feb) and the fifth (10 Mar.) sowing dates, respectively. A delayed planting from 21th Dec. declined the grain yield at a rate of 10 kg.ha-1 per day. The results for the triple interactive effects of cultivar × planting date × year showed that the highest grain yield was achieved in the first year × first sowing date (21th Dec. × the genotypes of Faraman and Goldasht with a mean yield of 2090 and 1758 kg.ha-1. Oil content was increased as the planting date was shifted from 21th Dec. to 10th Mar. The oil percentage at the first sowing date (21th Dec.) relative to the fifth sowing date (10th Mar,) increased by about 9% and among the cultivars, Padideh and Golmehr had 9% and 6% more oil content than Goldasht and Faraman, respectively. Seed yield showed the highest positive and significant correlation coefficient with number of boll per plant (r = 0.76 **), number of grain per boll (r = 0.75 **), and 1000-seed weight (r = 0. 47 **).

Conclusion:
Losing the appropriate planting date for winter cultivation system of safflower, shifting from early January to early February, can lead to a compensatory seed yield production. In fact, at these dates, suitable environmental conditions facilitate increased duration of vegetative growth and the formation of higher yield components such as number of florets per boll, boll per plant and grain per boll as compared to late planting date. Among the studied cultivars, Faraman and Goldasht produced the highest grain yield at the all planting dates, maybe due to the higher number of grain per boll and 1000-seed weight. To achieve maximum grain and oil yield in winter safflower cultivation for the conditions of Sistan region, sowing from early January (first date 21th Dec.) to late January (second date (9th Jan) using early maturity cultivars, such as Faraman and Goldasht cultivars is recommended.